Generally, display windows are installed so that an item displayed therein can be seen from the outside. To this end, a display window is formed using a transparent glass wall. For example, display windows can be installed in a shop, a department store, an art gallery, a museum, and the like. Such display windows are intended to display goods and to draw people's attention. For this reason, a manager may change the arrangement of items in a display window in order to effectively draw people's attention.